The present invention relates to a piezoelectric fluid ejecting device, such as an inkjet printhead and methods of manufacturing the same. More particularly, the present invention relates to fluid ejecting devices in which the drop volume can be modulated.
There is a need for a piezo-electric printhead in which drop volume can be modulated. Desirably, such a printhead is configured to permit ready access to internal as well as external contacts between the actuators and electrodes. Most desirably, such a printhead can be fabricated in a xe2x80x9cstackedxe2x80x9d configuration to achieve high resolution print quality. It is also contemplated that such a device can be used to eject fluids other than ink, such as adhesives and the like. The present invention meets the above needs and has additional benefits as described in detail below.
In one embodiment, this invention achieves fluid drop formation and ejection with multiple actuators within a given fluid chamber. Each actuator is permitted to deform in multiple directions that all contribute to chamber volume change and ejection of the drop. In a current embodiment, such a device is configured for formation and ejection of ink drops. Other fluids are, however, contemplated, such as adhesives and the like.
Additionally, the multiple actuators can be selectively deformed to vary drop volume to achieve, for example, gray-scale printing. Varying drop volume during printing has to date been difficult to achieve for most ink jet printing methods, including thermal ink jet printing. The multiple actuators also allow for large print height without stitching.
Further, the instant invention does not require a diaphragm, which often is fragile and is a common source of failure in piezoelectric printheads. In typical piezoelectric printheads, the diaphragm is made of a pliable material and is connected to a piezoelectric element. When the piezoelectric element changes shape in response to a signal, it manipulates the diaphragm, which causes a pressure wave to propagate through the ink chamber and results in the ejection of ink through an orifice.
Additional benefits of one or more embodiments of the present invention include a highly integrated structure for low cost manufacturing, an easy-to-stack design for high-resolution printing, few or no thermal expansion issues between the piezoelectric material and a diaphragm, and excellent ink compatibility and corrosion resistance.
In one embodiment, the present invention contemplates an inkjet printhead including a piezoelectric module having a plate with an integrated ink chamber in flow communication with an integrated ink supply manifold and an integrated ink orifice. The ink chamber includes a main channel that connects the ink supply manifold to the ink orifice, and multiple piezoelectric actuators that depend from the main channel and are spaced apart by ink subchannels that are in flow communication with the main channel. This embodiment further includes a ground electrode that is in contact with a first end of each of the actuators and a cover plate that is bonded to the piezoelectric plate. The cover plate seals the chamber and the manifold. The cover plate is in contact with a control electrode and is configured to conduct control signals from the control electrode to the actuators.
This and alternative embodiments of the present invention can also include one or more of the following features: the piezoelectric module can include multiple ink chambers disposed on the piezoelectric plate, with successive chambers being separated by a chamber wall; the ink chambers can be in flow communication with a common ink supply manifold; the chamber walls can be separated by a cut between successive chambers.
An elastic membrane can be disposed between the cover plate and the piezoelectric plate. The elastic membrane can be electrically conductive, or parts of the elastic membrane can be electrically conductive based upon the arrangement of the actuators. The actuators can be selectively activated to modulate ink drop size. A restrictor can be disposed between the manifold and the main channel.
Multiple modules can be stacked together on the printhead. The stacked modules can be offset from each other. The actuators can be disposed perpendicular to the main channel. The actuators can be elongated toward the ink orifice. The first end of each actuator can tapered. The actuators can be shorter than the surrounding chamber walls. The actuators can be arranged parallel to each other.
In another embodiment, the present invention contemplates an inkjet printhead having means for piezoelectric actuation capable of both vertical and horizontal deformation in direct communication with means for supplying ink from an ink manifold to an ink ejection orifice and control means for supplying a signal to the piezoelectric actuation means.
The inkjet printhead also can include means for restricting the flow of ink between the ink supply means and the manifold. The inkjet printhead also can include multiple piezoelectric actuation means stacked together on a single printhead. The stacked actuation means also can be offset from each other.
In another embodiment, the present invention contemplates a method of controlling ink drop volume in an inkjet printhead including the steps of
selectively activating one or more piezoelectric actuators in an array of piezoelectric actuators in direct communication with an ink supply to create a pressure wave that propagates through the ink supply and ejects an ink drop the volume of which is dependent on the number of actuators that are activated.
In this method, the actuators can be selectively activated by a control electrode electrically connected to the actuators. An electrically conductive elastic membrane also can conduct signals from the control electrode to the actuators to selectively activate same.
In another embodiment, the present invention contemplates an inkjet printer having a piezoelectric printhead as described above.
These and other features and advantages of the present invention will be readily apparent from the following detailed description, in conjunction with the claims.